During manufacture and/or filling of containers, various flaws can occur. For instance, in the case of glass containers such as glass vials, chips and cracks can occur in the containers themselves, and these chips or cracks can result in glass particles or glass shards being included in the interior of the container. In the case of plastic containers, splits, folds, or other discontinuities can occur during moulding of the container. Other flaws can also occur in the contents of containers of any type: foreign objects may be incorporated due to manufacturing errors, and in the case of containers containing food products, agglomerations of bacterial or fungal matter can occur due to microbial contamination. Another example of such flaws in the contents of containers are bent or broken needles in filled syringes. Such flaws can be detected in closed or open containers, whether filled or unfilled.
It is noted that for the purposes of this specification, the term “flawed container” is to be understood as comprising the case in which the container itself contains a flaw, or in which the contents of the container contains a flaw, or both.
It is important to be able to detect such flaws on a production line to prevent potentially harmfully-flawed or even dangerously-flawed products from reaching the consumer.
Visual inspection, or optical-based methods are only suitable for transparent containers, and inspection of the bottom corners of the interior of containers is made more difficult by optical distortion and refraction caused by the material and shape of the container. The container bottom is typically thick, non-planar, and of non-constant cross-section. Nevertheless this is the most critical portion to be inspected due to foreign objects typically accumulating there. Hence over the years, many different approaches for detecting such flaws have been developed using x-rays, which penetrate glass and plastic irrespective of its optical properties in the visible spectral range. Most materials have a degree of opacity to x-rays, enabling flaws including discontinuities and so on to show up on x-ray transmission imaging. For instance in the case of a glass vial with a crack, the discontinuity caused by the crack will reflect and/or refract the x-ray radiation, which can then be detected. Likewise, a thin section in a plastic container will absorb less x-ray radiation than a thicker section, and will thus be detectable. Furthermore, foreign objects in the container contents will reflect and/or refract and/or absorb x-rays and will likewise be detectable.
Several prior art flaw detecting methods and systems for containers using x-rays are discussed below:
EP 0 604 302 shows a method of x-ray analysis of objects passed on a circular track between an x-ray source and a single detector consisting of a conversion screen and a camera. This method would appear to result in low throughput of objects and poor resolution. Furthermore, the base of the objects will be poorly imaged, since the edges of the track overlap the bases of the objects.
U.S. Pat. No. 6,005,912 shows a method of x-ray analysis of containers incorporating two perpendicular x-ray sources (which may be constituted by a single source emitting two discrete beams) placed at 45° with respect to a line of containers being conveyed between the x-ray sources and respective detectors. Thus two images are taken of each container at 90° of rotation from each other. However, the x-ray source is disposed at the level of a conveyor belt which does not give good coverage of the base of the containers.
U.S. Pat. No. 7,164,750 presents an improvement to the method of U.S. Pat. No. 6,005,912 by situating the x-ray source above the plane of the conveyor so as to achieve improved imaging of the inside of the base of the containers.
U.S. Pat. No. 7,106,827 improves on the above by utilising obliquely-emitted x-rays originating from above and/or below the plane of the base of the containers presented on a linear conveyor belt, so as to better image the inside of the base of the container for the presence of foreign objects. However, a portion of the x-rays must pass through the conveyor belt, which reduces the imaging quality.
Finally, U.S. Pat. No. 4,989,225 shows a CAT scanner for creating dynamically-computed tomographic x-ray images of containers. In one embodiment, containers are passed on a circular path between an x-ray source at the geometric centre of the circular path and a sensor, the containers being additionally rotated around their own axes.
An object of the present invention is thus to overcome at least one of the above-mentioned disadvantages of the prior art, and thereby to provide a system and method for detecting flaws in containers and/or their contents which permits improved detection and higher throughput.
This object is achieved by a system for detecting flaws in containers and/or flaws in their contents, comprising a transport arrangement comprising a transport test path for transporting the containers, the transport test path being arc-shaped about an axis and defining a plane perpendicular to this axis for the movement of the outer surfaces of bases of the containers, i.e. when in use, the outer surfaces of the bases of the containers will travel along this plane. An x-ray source is disposed on the aforementioned axis, and a plurality of imaging x-ray detectors each having a sensing surface, i.e. x-ray detectors capable of forming an image based on received x-ray radiation, are arranged about the axis. By “sensing surface” we understand the surface of a detector which converts x-ray radiation into signals (as in the case of a semiconductor-type direct x-ray detector) or into another type of radiation that will itself be detected (as in the case of a scintillator plate converting x-ray radiation into visible light which is then itself detected by a digital camera or similar). The plurality of detectors permits imaging the containers being tested at various angles so as to obtain good coverage of the containers, and to achieve a good rate of throughput. The plane, x-ray source, and sensing surfaces are arranged such that, when considering each x-ray detector, a straight line which intersects the x-ray source and the x-ray detector in question intersects the plane such that the distance along the line from the x-ray source to the plane be shorter than the distance along the line from the plane to the sensing surface of the x-ray detector in question. Since this line intersects the plane, the x-ray source and the imaging x-ray detectors are situated on opposite sides of the plane. This geometric arrangement ensures good imaging at the detectors since it results in a good degree of magnification of the containers at the imaging x-ray detectors. Furthermore, the system comprises a processing unit with inputs operationally connected to outputs of the imaging x-ray detectors and itself having an output for a signal dependent on x-ray imaging by the imaging x-ray detectors. This output is operationally connected to a control input of a rejection mechanism for rejecting containers detected as having flaws in the containers themselves or in their contents. This combination of features enables accurate testing of containers with a good rate of throughput.
In an embodiment, which may be combined with any subsequently addressed embodiment unless in contradiction, the above-addressed straight line is normal to the sensing surface of the respective imaging x-ray detector. By thus arranging one possible straight line to be drawn as described, distortion at the imaging x-ray detector is minimised.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, the x-ray source is tailored to emit x-rays on a single arc, i.e. an unbroken arc. This eliminates the requirement for multiple x-ray sources or complex and potentially fragile shuttering of the x-ray source, thus decreasing complexity and increasing robustness of the system.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, the single arc has an opening angle of at least 180°, or of at least 220°, or of at least 270°, or of 360°, as considered in the previously mentioned plane. This permits the radiation to be emitted towards detectors over a wide arc, enabling the use of a large number of detectors in cooperation with a single source.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, the distance along the previously mentioned line from the x-ray source to the plane is at most 80%, or at most 60%, or at most 40%, or at most 20% of the distance along that line from the plane to the respective sensing surface. This allows the skilled person to tailor the geometry to achieve the best compromise of magnification and image clarity.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, the transport arrangement comprises a plurality of container supports each arranged to contact the base of the container over at most 50% of the area of the base of the container. This ensures that the edges of the base are kept free from interference with the container support, thus maximising the accuracy of the imaging especially of the inside bottom corners of the containers.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, the transport arrangement comprises a plurality of container supports each arranged to hold the top of the container, which on the one hand, when used on their own, permits the base of the container to be kept completely free, e.g. in the case when the supports are hanger supports, or on the other hand, when used in combination with supports contacting the container bases, permits a very stable supporting arrangement for the containers.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, at least some of the container supports are movable in a direction parallel to the addressed axis, i.e. up and down. This provides one mechanism by which the transport arrangement can pick up containers from e.g. an inlet section of the transport arrangement, such that they can be transported along the transport test path of the transport arrangement.
In an embodiment, which may be combined with any previously or subsequently addressed embodiment unless in contradiction, at least some of the container supports are rotatable about support axes parallel to the addressed axis, e.g. about their own central axes. This enables the containers to be presented to the detectors at different angles so as to image as much of the containers as possible.
Furthermore, the object of the invention is resolved by a method of detecting flaws in containers and/or in their contents, comprising transporting the containers along a transport test path, the transport test path being arc-shaped about an axis and defining a plane perpendicular to said axis for the outer surfaces of bases of said containers, i.e. the plane is defined by the passage of outer surfaces of the bases of the containers as they travel. X-ray radiation is emitted from an x-ray source disposed on the addressed axis, and the emitted x-ray radiation is received at a plurality of imaging x-ray detectors (i.e. x-ray detectors capable of forming an image based on received x-ray radiation) arranged about said axis and having respective sensing surfaces. The plurality of detectors permits imaging the containers being tested at various angles so as to obtain good coverage of the containers, and to achieve a good rate of throughput. The addressed plane, x-ray source and sensing surfaces are mutually arranged such that a respective straight line which intersects the x-ray source and a respective sensing surface intersects the plane such that the distance along the line from said x-ray source to the plane is shorter than the distance along the line from the plane to the respective sensing surface, i.e. the x-ray source and the x-ray detector are disposed on opposite sides of the plane. Images received by the imaging x-ray detectors are processed so as to determine the presence or absence of one or more than one flaws in the container and/or its contents, and the results are assigned to the respective containers. Containers determined as having one or more flaws therein or in their contents are rejected. This method enables accurate testing of containers with a good rate of throughput.
In an embodiment of this method, which may be combined with any subsequently addressed embodiment of the method unless in contradiction, the x-ray radiation is emitted on a single arc. This eliminates the requirement for multiple x-ray sources or complex and potentially fragile shuttering of the x-ray source, thus decreasing complexity and increasing robustness of the system.
In an embodiment of this method, which may be combined with any previously or subsequently addressed embodiment of the method unless in contradiction, the single arc has an opening angle of at least 180°, or of at least 220°, or of at least 270°, or of 360°, considered in the previously-mentioned plane. This permits the radiation to be emitted towards detectors over a wide arc, enabling the use of a large number of detectors and a single source.
In an embodiment of this method, which may be combined with any previously or subsequently addressed embodiment of the method unless in contradiction, the distance along the previously mentioned line from the x-ray source to the plane is at most 80%, or at most 60%, or at most 40%, or at most 20% of the distance along the line from the plane to the respective sensing surface. This allows the skilled person to tailor the geometry to achieve the best compromise of magnification and image clarity dependent on the specific application.
In an embodiment of this method, which may be combined with any previously or subsequently addressed embodiment of the method unless in contradiction, the containers are transported by a transporting arrangement comprising a plurality of supports each arranged to contact the base of a container over at most 50% of the area of the base of the container. Thereby the edges of the base may be kept free from interference with the container support, thus maximising the accuracy of the imaging of the inside bottom corners of the containers.
In an embodiment of this method, which may be combined with any previously or subsequently addressed embodiment of the method unless in contradiction, the containers are transported by a transporting arrangement comprising a plurality of container supports each arranged to hold the top of the container, which on the one hand, when used on their own, permits the base of the container to be kept completely free, e.g. in the case when the supports are e.g. hanging supports, or on the other hand, when used in combination with supports contacting the container bases, permits a very stable supporting arrangement for the containers.
In an embodiment of this method, which may be combined with any previously or subsequently addressed embodiment of the method unless in contradiction, the containers are transported around the transport test path at continuous speed or in a stepwise manner. This presents various operating possibilities, stepwise transport particularly enabling clarity of imaging since the containers can be imaged when stationary.
In an embodiment of this method, which may be combined with any previously or subsequently addressed embodiment of the method unless in contradiction, the containers are rotated about their axes. This can be either at constant angular velocity or stepwise while the containers are transported along the transport test path. This permits imaging the containers from a plurality of angles in a plurality of orientations so as to obtain good coverage of the containers and to reduce the risk of non-detection of a flaw, and also permits tomographic 3-D imaging of the containers.
Finally, the invention relates to a method of manufacturing flaw-free containers, i.e. containers with no detectable flaws in the containers themselves or in the contents thereof, comprising manufacturing filled or unfilled untested containers—this manufacturing possibly also comprising filling of the containers—then testing the containers by any of the above-mentioned methods of detecting flaws. Containers which have not been detected as having flaws therein or in their contents are then accepted as being manufactured flaw-free containers. Containers which have been detected as having flaws therein or in their contents are rejected. This permits reliable manufacture of flaw-free containers.